The present invention relates to the sweep circuitry of cathode-ray tubes and particularly to a circuit for stabilizing the operating voltage acting on the sweep transformer in the sweep circuit of a cathode-ray tube, more particularly for the line sweep circuit in a television receiver.
It is known that the line sweep output stage of a television receiver requires a stabilized operating voltage to produce a sufficiently constant sweep amplitude, even in the presence of a fluctuating mains, or supply, voltage. The circuit provided to produce the stabilized operating voltage must be able to dissipate the energy resulting as the difference between the two extreme modes of operation with minimum and maximum possible mains voltage and an approximately uniform current consumption. This energy to be handled by the current supply circuit is particularly high in color television receivers since these instruments require an operating current for the sweep circuit which is about three times greater than that required in black and white television receivers.
The use of a power supply unit including, for example, a regulated series transistor for this purpose is not possible without difficulty since currently available power transistors cannot process such high leakage energies without danger. Moreover, it would be necessary to use expensive transistors with very large cooling bodies, which is uneconomical.
Other power supply units, such as controlled thyristor power units for example, require additional measures, such as a choke for example, to reduce switching peaks in the thyristor, and such additional measures involve relatively high expenditures.